Orifice with Pressure-Dependent Flow
Orifice with pressure-dependent flow rate
Description
Equations
Variables
Connections
Parameters
The Orifice with Pressure-Dependent Flow (or Orifice Pressure Dependent Flow) component uses a user-supplied table to define the flow rate for a given pressure drop. It is a general two-port component and not restricted to be an orifice but is labeled as such and given an appropriate icon for the user's convenience. A similar part is also available as a check valve and a relief valve.
The flow rate through the component is computed as a function of the pressure difference between port A and port B from a data table containing values of pressure difference vs the corresponding flow rate.
If q−p=−qp, then the symmetric parameter can be assigned true and only the first quadrant of the q vs p curve needs to be defined in the table.
Pressure vs Flow Rate
For this component, the flow rate must be specified as a function of the pressure difference in the form of a table. The following parameters allows users to specify the necessary data for this calculation.
Data Source: This parameter allows users to specify the nature of the source file for the Pressure vs. flow rate table. The available options are file, attachment, and inline.
file: Use this option to specify a source file (an Excel or a CSV file) located on the hard drive. Use the qdP parameter to browse to and/or select the data file. The data file will not be attached to the MapleSim model.
attachment: Use this option to specify a data file (an Excel or a CSV file) that is attached to the MapleSim model. To be used as an attachment, data files must be attached to the MapleSim model and be categorized under Data Sets. The attached files in a MapleSim model can be viewed in the Attachments pane under the Data Sets section. For more information, see Attaching a File to a Model. If the required file is not already attached to the MapleSim model, use the qdP parameter to attach a new file.
Note:
If the file option is used, subsequent changes to the source file will be incorporated into MapleSim simulations
If the attachment option is used, subsequent changes to the source file will not affect the version attached to the MapleSim model. To ensure updates to the source files are incorporated in the simulation, the file must be reattached.
The Data Generation App can be used to generate table data from mathematical functions using Maple code. For more information about MapleSim apps, see Using MapleSim Apps.
inline: Use this option to directly specify the pressure vs. area relationship in the form of a table. In the qdP parameter, enter an m×2 matrix. The first column must contain values of pressure difference and the second column must contain corresponding values of the area.
Note: To change the dimensions of table, right-click (Control-click for Mac®) the parameter field and select Edit Matrix Dimensions. In the Matrix Dimensions dialog, enter values for the number or rows and columns and then click OK.
Skip rows: This option allows users to specify the number of top rows to be ignored during the calculations. This option can be useful when the Excel file contains header information.
Smooth: The smooth option specifies how the data table is interpolated.
Pressure difference unit: This option specifies the unit of pressure used in the supplied data.
Flow unit: This option specifies the unit of flow rate used in the supplied data.
Optional Volumes
The boolean parameters Use volume A and Use volume B, when true, add optional volumes VA and VB to ports A and B, respectively. See Port Volumes for details.
If two orifices or valves are connected, enabling a volume at the common port reduces the stiffness of the system and improves the solvability.
p=pA−pB
q=qA−qVA=−qB+qVB={signpsymmetric1otherwise⋅Interpolate1DqdP,{psymmetricpotherwise⋅pressUnit,2,smoothness,skipRows
qVA={dVfAdt\seVolumeA=true0otherwiseqVB={dVfBdt\seVolumeB=true0otherwise
VfA={VA1+pAEl\seVolumeA=true0otherwiseVfB={VB1+pBEl\seVolumeB=true0otherwise
Name
Value
Units
Modelica ID
p
Pa
Pressure drop from A to B
q
m3s
Flow rate from port A to port B
qsummary
qflowScaleSummary
Internal flow sensor
q_summary
dpsummary
ppressScaleSummary
Internal pressure difference sensor
dp_summary
portA
Upstream hydraulics port
portB
Downstream hydraulic port
Flow Rate Vs. Pressure
Default
symmetric
true
True (checked) the data for positive pressure difference used for both directions
Data source
inline
datasourcemode
qdP
100.,0.001
Data set
table
Skip rows
0
Number of rows to skip
skipRows
Smooth
Smoothness of table interpolation
smoothness
Pressure difference unit
kPa
Unit of pressure used in the data
pressUnit
flowUnit
cm2
Unit flow rate used in the data
useVolumeA
false
True (checked) means a hydraulic volume chamber is added to portA
VA
1·10−6
m3
Volume of chamber A
Va
useVolumeB
True (checked) means a hydraulic volume chamber is added to portB
VB
Volume of chamber B
Vb
For more information see Port Volumes.
See Also
Hydraulics Library
Restrictions
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